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I recently had an addition put on over the garage (520 sq ft). I did a heat load calc on the space and oversized the unit by 20%. Based on this I chose a Mitsu 15K heat mini split (I did not want to go larger to prevent short cycling in the summer). My only concern was that I live in MA and the temps in the winter often get below freezing, teens. The contractors that I had over said it would be no problem. After this winter when the temps dropped below zero, the heat pump seemed to do fine. My question is I know below 32 the heat pumps loose output. I am not sure if the unit ran all the time to keep up but is this the most efficient source of heat for a small space. I did not want to go electric as KW/H in MA is 13 cents. Should I look into some supplemental heat for the really cold days? If so any recomendations?

Mitsu Heat Pump

Bills were a bit high but hard to tell as there was construction going on for most of the winter and it was really cold. I currently have a gas 3 zone furnace with A/C/. Unfortunately the unit was too far away to be able to branch a line and its capacity was questionnable. Someone mentioned a gas or pellet stove. Easy to vent and 85+ efficient?

Are you sure your model doesn't have electric strip backup? Mitsu makes one model that has it. Without getting into too much expense, I just might get an electric BB just for those few days some winters when you go below zero. Any thought to a gas direct vent fireplace or wall heater? Checkout http://www.cozyheaters.com

wHY NOT USE A GAS HEATER. YOU ALREADY HAVE THE GAS TO THE HOUSE. pELLET STOVE, WOOD STOVES ARE NICE BUT YOU NEED TO CLEAN AND ADD FUEL ALL THE TIME. A GAS FIRE PLACE WITH A REMOTE THERMOSTAT WILL BE JUST FINE.